This proposal aims to investigate the relationship between the anatomical and functional plasticity of mammalian brain using ocular dominance plasticity in mouse visual cortex as a model system. Occluding an eye during early postnatal development leads to a rapid loss of vision through the deprived eye. The location and means of synaptic change in ocular dominance plasticity is a major outstanding problem in systems neuroscience. Recent evidence suggests that the earliest changes occur in the superficial layers (layer ll/lll) of primary visual cortex where some connections appear to rewire on a rapid timescale (< 2 days). By using new imaging techniques that facilitate the chronic imaging of single axons in the living brain, I aim to investigate further the hypothesis that visual deprivation stimulates a rapid rearrangement of synaptic connections in layer ll/lll. At the same time, I will use intrinsic signal imaging to keep track of the ocular dominance of the cortical territory containing the axons of study. I plan to apply these techniques to study the role of inhibition in opening the critical period for ocular dominance plasticity. Altogether, it is likely that this work will help elucidate the anatomical underpinnings of cortical plasticity. [unreadable] [unreadable]